1. Field of the Invention
The present invention relates to a structure of semiconductor including nitride which emits lights due to a transition of band-to-band of an active layer.
2. Related Background Art
Because an optical transition of semiconductors including a gallium nitride, i.e. InAlGaN, is a direct transition, it is possible to allow lights to efficiently emit and recombine. Furthermore, because a transition energy of the semiconductors including a gallium nitride is widely ranged from 2 to 6.2 eV, the semiconductors are developed as efficient light emitting device materials such as a semiconductor laser or a high-luminance visible LED (Light Emitting diode). Furthermore, semiconductors including gallium nitride has a feature that it is possible to emit lights at an ultraviolet wave length as III-V compound diodes. Accordingly, it may possible to replace conventional ultraviolet luminants with the semiconductors including gallium nitride.
A band-gap energy of InxGa1-xN, which is one type of the semiconductors including gallium nitride, is variable by changing an indium (In) composition x. Because of this, it is possible to use the InxGa1-xN as an active layer for avisible light emitting device.
At this time, a LED, of which a light emitting layer is a mix crystal made of InGaN, is realized, and a semiconductor laser which oscillates by a current injection is realized.
However, an optical mechanism of the LED, of which the active layer is formed of a crystal that a constituent ratio x is high, where x is equal to or less than 0.05, is different from the optical mechanism of a crystal that the constituent ratio x is low. In order to realize efficient ultraviolet LED, it is desirable to improve electric properties by improving a method for allowing the crystals to grow and an device structure.